Detectors proportionality

Correction for efficiency of the detector, number of events generated by a single photon, detector proportionality, etc, all of which must be precise and reproducible. 

Similarly to Eq. (2.6), fCis a proportionality constant containing fixed operating conditions, for example incident electron current density, transmission of the analyzer at the kinetic energy Ea, efficiency of the detector at the kinetic energy Ea, and the probability of the Auger transition XYZ. 

The flow rate term is kept independent of the proportionality constant to allow for separate adjustment of the flow rate without the need to readjust the calibration factor for the detector. 

Thus, the scalers on the dosimeter module may be set to display in mCi of Rb-82, since the circuit incorporates an adjustable pulse divider corresponding to the proportionality constant. In addition to displaying the activity of Rb-82 passing the detector at any instant, the second scaler provides a summation of total activity eluted. The flow rate constant, F, is set equal to the flow rate control of the infusion pump. 

JET. The diameters of most jets used today are roughly 0.5 mm. This is because of the type of flame used. In a diffusion flame, as opposed to a flame in which the oxidizer and fuel are premixed, the rate of diffusion of the two gases controls the rate of burning. The velocity of the gas flow out the jet must be set to match the rate of diffusion. If the jet diameter is a little different from 0.5 mm, the detector can be optimized at a proportionately different flow. Much beyond a factor of two differences in diameter leads to some other effects, such as thermal transfer or flow stability problems. 

The recovered lemon oil samples were analyzed by gas chromatography. A 0.5 mm i.d. x 30 m thin film (0.1 pm) SE-30 glass capillary column (Supelco, Inc., Bellefonte, PA) was used with a flame ionization detector. The temperature was programmed from 348 to 473 K. Peak identification was based on information of Supelco, Inc., A. M. Todd Company, and Staroscik and Wilson (] ). Staroscik ( ) provided us with the response values used in his work and we assumed that our detector would give proportionate responses. Staroscik found in his work that relative standard deviations of the response values were generally less than 3%. 

Equation 1 shows the relationship of sample collection, preconcentration, and detection in the portal. This equation contains measurable parameters such as (i) sample removal and transport from a person, (ii) collection (adsorption) and release (desorption) of the explosive in the preconcentrator, (iii) additional preconcentration, if applicable, (iv) a term that accounts for flow mismatches between the detector inlet and the preconcentrator subsystem outlet, and (v) a proportionality term relating signal strength to concentration at the detector. 

If the detector response is linearly proportional to the concentration of solute in the column effluent, there is also a linear proportionality between the peak area and the total mass of solute in the eluted chromatographic zone. Hence, for the peak areas of the compound under determination, i, calibration standard s and the reference compound r (cf., the definition of the relative specific response), Ai, As andAr, respectively, we have... 

These detectors also differ in their primary group classification. TCD is a concentration-sensitive detector, which means it records the proportionate concentration of an analyte in the mobile phase (ng/mL), while the FID is a mass fiow detector, which means it records the measured mass of a particular component per unit time (ng/s). Though FID is more suitable than TCD, often, the mass spectrometer is used due its superior detection abilities. Instead of passing through the detector within the GC, separated samples are transported to the mass spectrometer and further analyzed. However, some studies use a combination of methods, where GC-FID is used in conjunction with GC-MS (Maatta et ah, 1999 Phillips et ah, 1999). 

The fluorescent intensity emitted at a given point in the sample per unit of mass and per incident photon is proportional to the concentration level of the element at that point. If there were no interaction between the radiation and the matrix (the environment surrounding the point under analysis), the intensity measured by the detector would be proportional to the concentration level of the element and the proportionality coefficient could be deduced fiomacieasur-ing the intensity on a reference of known composition under the same operating eonditions. 

Instrumental aspects For many methods of kinetic analysis, direct proportionality between signal and concentration is most easily obtained if the extent of reaction is kept small. This leads to instrumental problems, since small changes should be measured with high precision. The development of detectors of high stabihty to meet this need is proceeding. ... 

Parris and coworkers calculated figures of merit for the various modes of operation studied with their atomic absorption detector utilizing the procedure of Mandel and Stiehler . The latter devised a simple quantitative measure of merit for comparing proportionality quantities such as these calibration curves. They define sensitivity as a criterion which takes into account not only the reproducibility of precision of the test procedure, but which is also diagnostic of small variations in the property measured. Thus,... 

The count rate is a measure of the rate at which individual radiation particles/ photons cause pulses in the detector. For this reason, proportional counters can be used to determine the amount of radioactivity in a sample. The proportionality of the detector can be used to distinguish between different radiation energies of types of radiation, based on pulse size. 

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